The present invention relates generally to hydraulic couplings for use in motor vehicle driveline applications. More specifically, the hydraulic coupling includes a hydraulic pump, a transfer clutch coupled between a pair of rotary members, and a fluid distribution system operable for controlling actuation of the transfer clutch.
Hydraulic couplings are used in a variety of motor vehicle driveline applications for limiting slip and transferring drive torque between a pair of rotary members. In all wheel drive applications, hydraulic couplings have been used to automatically control the transfer of drive torque from a driven member to a non-driven member in response to speed differentiation therebetween. In limited slip applications, such as used in association with a differential in an axle assembly, full-time transfer case, or transaxle, hydraulic couplings have been used to limit slip and bias the torque split between two rotary members. Examples of known hydraulic couplings which are adaptable for such driveline applications include viscous couplings, geared traction units, and passively and electronically-controlled hydraulically-actuated friction clutches generally similar to those shown and described in U.S. Pat. Nos. 5,148,900, 5,358,454, 5,649,459, 5,704,863 and 5,779,013.
Due to the advent of increased consumer demand for motor vehicles with traction control systems, hydraulic couplings are currently being used in a variety of driveline applications. Nevertheless, such hydraulic couplings are still susceptible to improvements that may enhance their performance and cost. With this in mind, a need exists to develop improved hydraulic couplings which advance the art.